Reverse voltage generation circuit

Abstract

An improved reverse voltage generation circuit is offered. The reverse voltage generation circuit can be formed in a single semiconductor substrate, prevents leakage current of constituting MOS transistors and stabilizes operation of the circuit. A first and a second charge transfer MOS transistors and a first and a second driver MOS transistors are formed in a surface of a P-type semiconductor substrate. The first charge transfer MOS transistor and the first and the second driver MOS transistors are of a P-channel type, and formed in a first N-well, a second N-well and a third N-well, respectively. The first, the second and the third N-wells are formed in a surface of a P-type semiconductor substrate. The second charge transfer MOS transistor is of an N-channel type and formed in the surface of the P-type semiconductor substrate. A power supply voltage is applied to a source of the first driver MOS transistor and an inverted voltage is generated and outputted from a drain of the second charge transfer MOS transistor.

Description

CROSS-REFERENCE OF THE INVENTION[0001]This invention is based on Japanese Patent Application No. 2004-042462, the content of which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates to a reverse voltage generation circuit that generates a voltage of the opposite polarity to an input voltage.[0004]2. Description of the Related Art[0005]The reverse voltage generation circuit is used as a power supply to an LCD (Liquid Crystal Display) driver circuit that provides an active matrix type LCD panel with gate signals, for example. The reverse voltage generation circuit generates a negative voltage (−15V) from a positive voltage (+15V), for example.[0006]FIG. 5 is a circuit diagram of a reverse voltage generation circuit according to prior art. The reverse voltage generation circuit is composed of a first and a second charge transfer MOS transistors TR21 and TR22 of an N-channel type, a first and a secon...

AI Technical Summary

Benefits of technology

This configuration stabilizes the operation and prevents leakage currents, enabling efficient generation of negative voltage from positive voltage, suitable for LCD driver circuits, and can also generate positive voltage from negative voltage by reversing transistor types and substrate.

Problems solved by technology

However, when the reverse voltage generation circuit of FIG. 5 is formed in the P-type semiconductor substrate, there arises a problem described below.

However, the output voltage is not yet generated at the time the power supply is turned on (at the beginning of the operation of the circuit).

As a result, the substrate voltage of the transistors is unstable when the power supply is turned on.

If the substrate voltage is somewhat higher than the ground voltage Vss, the transistor with its source connected to the ground voltage Vss is back-gate biased with a reverse voltage, leading to a reduction in a threshold voltage and possibly to causing a leakage current in the transistor.

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